1. Field
Apparatuses consistent with exemplary embodiments relate to a zoom lens and a photographing apparatus including the same.
2. Description of the Related Art
Photographing apparatuses, such as surveillance cameras including a solid state imaging device, such as a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS), video cameras, digital cameras, or the like are widely used. Photographing apparatuses need to have a high performance and be small-sized. Thus, zoom lenses used in photographing apparatuses also need to have a high optical performance and be small-sized.
As an example of zoom lenses used in photographing apparatuses, a rear focusing zoom lens including a first lens group having a negative refractive power and including a negative lens and a positive lens and having at least one aspherical surface, a second lens group having a positive refractive power, a third lens group having a positive refractive power, and a fourth lens having a positive refractive power, wherein the first lens group, the second lens group, the third lens group, and the fourth lens group are sequentially arranged from an object side to an image side, and wherein, simultaneously, zooming is performed by moving the second lens group in an optical axis direction, a variation in an image plane caused by zooming is corrected by moving the fourth lens group in the optical axis direction, and focusing is performed, is widely used.
In the rear focusing zoom lens, an effective diameter of the first lens group may be made relatively small compared to that of a zoom lens that performs focusing by allowing the first lens group to move in the optical axis direction, and thus the entire lens system may be easily minimized. Also, since close focusing can be performed and a comparatively small and light-weight lens group is moved in the optical axis direction, the rear focusing zoom lens can quickly focus on a subject by using only a small amount of driving power.
As the sizes of pixels are greatly reduced due to a solid state imaging device having a small size and a large number of pixels, a small-sized zoom lens having high optical performance and a short overall length of a lens is required. However, in order to obtain high optical performance, the number of lenses needs to be increased, and the overall length of the lens needs to be increased. Thus, it is difficult to make a small-sized zoom lens.
Also, in order to make a small-sized zoom lens while increasing a zooming rate of the zoom lens, a variation in aberration caused by zooming increases, and thus it is difficult to obtain good optical performance from a wide angle end to a telephoto end. In particular, in a zoom lens having a high zooming rate, it is difficult to correct spherical aberration at the telephoto end. Also, as the size of the zoom lens becomes small and a zooming rate thereof increases, the amount of aberration of an actuating lens group increases.